Dualism is the belief that there are separate physical and
non-physical aspects of reality. This leads to the famous mind-body
problem: if part of us is physical, and part non-physical, how do they
interact? "Where" are they connected?

I don't claim to have the answer to that (although I do have
a thought
or two about it), but think it's still better
than the other main alternatives: Idealism and Materialism/Physicalism/Scientism.

Idealism says that nothing actually physically exists. It's all some
kind of illusion we (or maybe just you!) are experiencing. Maybe
nothing except you exists. Repeatable experiments are basically just
God or the universe pulling our (your?) legs.

Materialism (currently very popular among scientists) says that
only the physical world exists. (Apparently the preferred term for
this among philosophers has been
Physicalism. And lately (2013) the word "Scientism" has come into broader use
to descibe a philosophy that includes this as one element.)
The problem with this is that people have no intrinsic
worth, relative to very complex, useful machines. If you think you're
in this category, but object to the proposition that computers will some day
be exactly the same as people, I think you're confused.

So, I believe that if one is both a scientist and believes in any kind
of spirituality, one is actually a dualist.